Blue light fends off drowsiness in the middle of the night, which could be useful to people who work at night.
240
Sleeping on your stomach can induce weirder, scarier, and sexier dreams.
22
Sea otters hold hands while sleeping so they don’t drift away from each other.
104
In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
13
The human brain is more active during sleep than during the day.
28
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23